1. Field of the Invention
The present invention relates generally to an optical film and a head-up display device having the same; particularly, the present invention relates to an optical film and a head-up display device having the same that can scatter images and increase the transmittance of external light.
2. Description of the Prior Art
Recently, more and more people area driving vehicles, and thus the expectation of vehicle equipment is getting higher and higher. Generally, driver watches the front road condition through windshield and gets information of vehicle condition from dashboard. However, the driver cannot pay attention to the front road condition while lowering his/her head and watching the dashboard. For instance, the driver cannot pay attention to both road condition and information of vehicle condition when the vehicle is moving at a very high speed.
Actually, current vehicle manufacturers utilize head-up display for aircraft on vehicles, so that drivers can get the information of vehicle condition without lowering their head. Particularly, the head-up display projects an image of the vehicle condition information on a coating film, which is disposed on the windshield. It is noted that the coating film can reflect the image of vehicle condition information and also allow external light to be transmitted therethrough.
However, the coating film generally does not have a preferable display effect. In practical applications, the transmittance of the coating film is not optimized, so that it is difficult for the driver to clearly watch the front road condition. In addition, part of the vehicle condition image is reflected on the coating film, and the rest part of the vehicle condition image is transmitted through the coating film. It is noted that the transmitted image is refracted on the inner surface of windshield and is reflected on the outer surface of windshield to be transmitted through the coating film because the windshield has a certain thickness, so that the driver will see two overlapping images. In addition, the vehicle condition image is reflected by the coating film to the eyes of the driver. In other words, the driver receives two reflected images. Once different drivers having different height use the head-up display, the driver needs to adjust the position and the laminating angle of the coating film on the windshield, so that the reflected images can totally transmitted to the view of the driver. For the above reasons, the conventional head-up display still has many defects.